Process for the manufacture of cup grease



Aug. 28, 1934. P. sUBKow PROCESS FOR THE MANUFACTURE 0F CUP GREASE Filed Sept. 28. 1931 INVENTOR.

Patented Aug. 28, 1934 PROCESS FOR. THE MANUFACTURE F CUP GREASE Philip Subkow, Los Angeles, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application September 28, 1931, Serial No. 565,681-

2 Claims.

The present invention pertains to a process for producing grease and particularly a cup grease having a soap base and mineral oil.

It is well known that a large percentage of the 5 present day greases are chiefly composed of semi-solid emulsions of lubricating oil and water stabilized by a soap. At present, practically.

all grease is produced from mineral oils.

The quality of the present day grease del0 pends,'to a great extent, on the lubricating qualities of the mineral oil used. In general, a poorly refined mineral oil fraction will result in a poor grease when mixed with Water and soap. On the other hand, a lubricating oil which is, perse, a good lubricant, will impart its ne qualities to the grease produced therefrom.

However, the nature of the soap with which the oil is mixed also plays an important part in the quality of the grease. The soaps used are of several types and are named after the alkali used to treat the fats. Thus, potash soaps, calcium soaps or soda soaps are prepared by reaction of fats with alkali of the foregoing elements. Soaps made from different types of fats have different properties. Some will readily form emulsions with mineral oils While others will not.

The Water content also has an important bearing on the quality of grease. Water is used in the preparation of the soap and, also, to emulsify the soap with oil. In the preparation of soap, sufcient quantity of Water must be present in the mixture of fats and hydrated lime forming the soap making ingredients to completely hydrolyze all of the glycerides present in the fat. With an insuiicient amount, free fat and/0r free lime will be present which will result in a poor quality of soap and, also, in a grease produced therefrom.

As previously stated, water is essential to emulsify the soap and oil to produce the grease. The amount of water used for this purpose is very small and it varies from 1 to 2.50%, depending upon the amount of soap used in the grease. A small variation of the water content from the correct amount will produce a grease which is not suitable for the market. Also, variation of the .water content from one batch to another will also vary the uniformity considerably. If the amount of water is insufficient, the grease will not be stable and the oil and soap 'will separate. If an excess of water is present, the grease will resemble a yellowish paste-like substance, which is not at all suitable as grease. Therefore, with such minute amounts of water in the finished grease, the control of the water content therein becomes an important item if a fine quality of grease and if repeated batches or similar uniformity are to be produced.

Perhaps the prime reason for the poor quality of grease heretofore produced is attributed to the 6G methods of manufacturing. In the past, grease has been produced by cooking a mixture of lime, an excess of water and a small amount of oil and the necessary quantity of fat in an open top steam jacketed kettle. The cooking was continued with agitation until the kettle operator determined that all of the excess Water was driven off and the hydrolysis or saponification completed. The mineral oil, and also the necessary amount of Water required for the emulsion, were then added.

However, unless great care is taken, the grease thus produced Will not be uniform. The kettle operator must judge when the soap stock has cooked long enough and when the mineral oil should be added. The addition of the correct amount of Water for the emulsion depends on the judgment of the operator. However experienced the operator may be, there are many circumstances which escape his observation. He S0 is not aided by accurate knowledge of the conditions of his batch of grease. For example, if the rate of evaporation during cooking is greater than anticipated by the kettle operator, the excess Water will be driven off before the saponification or hydrolysis reaction has been completed. This will result in the production of soap containing free fatty acids and/or alkali which are objectionable in the grease produced therefrom. l

In more recent years, saponication of the soap stock has been carried out under pressure in order to prevent evaporation of the excess water during the cooking operation. Thus, the fats, lime and water and in some cases a small amount of oil to prevent the soap from getting too stiff, are subjected to'cooking in an agitated, steam jacketed kettle provided with a pressure tight cover. During the cooking, the pressure developed inside the kettle will approximate 70 to 85 pounds per square inch. When it is determined that the saponification reaction has been completed, the soap in the kettle is blown out by its own pressure into a large open mixer where the compounding or mixing operation is carried out.

During the discharge of the soap into the open mixer, the excess water is lost by the reduction in pressure to atmospheric, leaving a soap which is nearly dry and to which the mineral oil and water for emulsication are added.

In the method stated above, a great amount of discretion' is left to the operator in determining the correct amount of water to be added during compounding of the soap with oil and water -so that repeated batches of uniform grease are difficult of production. The evaporation of the water is not under accurate control and the amount of water that must be subsequently added is a variable factor and must be left to the judgment and skill of the operator without scientific guide. Furthermore, the method has the great disadvantage that when the soap from the pressure kettle is discharged into the open mixer, a large quantity of the soap splatters on the sides of the mixer and hardens quickly so that when it is scraped into the mixer proper and mixed with oil and water, lumps of the soap will be present in the grease unless care is taken to prevent this. Another disadvantage is apparent in the prolonged time required for scraping the splattered soap from the sides of the mixer and also in reducing or disseminating the soap in the oil and water.

In another known method of preparing grease under pressure, all of the mineral oil for the finished grease, as Well as the' materials forming the saponication charge, such as fats, lime and water, are cooked in the pressure kettle for a period of time. The contents are then permitted to cool before the internal pressure is released so as to prevent escape of moisture. The contents are then permitted to stand for a period of time in order to permit stratification of the excess water, whereupon this is removed. However, this method has the disadvantage that the cooking must be carried out for a longer time, due to the dilution of the saponiflcation charge with the large quantity of mineral oil, which slows up the reaction considerably. Also, the grease produced is usually saturated with excess water. Consequently, this process does not permit the production of various grades of grease.

It has now been found that many of the above difficulties and disadvantages attending prior methods of producing grease are due primarily to the lack of control of the moisture content either during the hydrolysis of the fats and alkali and/or during compounding with the mineral oil. By the present invention, the moisture content is accurately controlled at all times.v Thus, in one method of carrying out the invention, the fats and hydrated lime are cooked with a predetermined amount of water necessary to completely hydrolyze or saponify the fats but without excess, and no moisture is permitted to escape during the saponification operation nor during the discharge into the open compounding kettle.`

The conditions of saponification are so controlled that the reaction is completed without using an amount of water greater than that necessary for the production of the particular grease being manufactured. The remaining portion of water for emulslcation is added during the mixing of the soap with the mineral oil. However, it is preferable to hydrolyze the fats and alkali ,with all the predetermined amount of water necessary in the finished grease but without excess so that the compounding with the mineral oil may be carried out without addition of water to bring the grease to the desired grade.

When the saponication reaction has been completed the contents of the pressure kettle may be permitted to cool below the evaporation temperature of water and then mixed with the proper amount of mineral oil. If all of the water necessary in the finished grease has been added to the initial saponication charge, none need be added during compounding. However, if only a portion has been added, the remaining portion is now added during the admixture with the mineral oil to bring the water content to the desired amount.

It is preferable to discharge the soap into the open mixer at the saponication temperature of the pressure kettle, i. e., Without permitting the soap to cool prior to the discharge and it has been found that by gradually discharging the soap under a bath of the oil, that the oil will absorb the soap and splattering on the sides of the kettle is entirely prevented. This will eliminate the necessity for scraping the kettle walls and also will permit a quicker distribution of the soap in the oil. Also, the grease produced in this manner will be free of hard lumps of incompletely dissolved soap. The addition of the soap to the oil permits of a more uniform distribution of the soap and water and produces a more homogeneous emulsion, i. e., grease.

Thus, with a better control of the moisture content during the production of'the soap as well as of the grease, a grease will be produced having a fixed moisture content which has an improved degree of uniformity from one batch to the next over that exhibited by the batches produced by prior methods. Furthermore, the invention comprehends a considerable saving in the time required for mixing the soap with oil. The time required by the present invention for reducing the soap with oil is decreased from approximately two hours to less than one hour in the case of a full sized commercial batch. A further saving in time is realized by the avoidance of scraping clean the agitator and kettle walls due to the splattering of the soap. l

Therefore, it is a primary object of this invention to provide a process whereby the water content of the soap, as well as of the finished grease, may be accurately controlled.

Another object resides in controlling the water content during hydrolysis or saponication of the fats and to provide suicient water for complete saponication but not more than that required in the finished grease. Another object is to prevent escape of water during saponiflcation and compounding with oil.

It is a further object to discharge the soap into the compounding kettle in such manner as to cause uniform distribution of the soap in the oil.

It is a further object of this invention to produce soap under pressure to avoid loss of water and then introducing the soap into oil under such conditions as will prevent loss of water and to cause a uniform grease to be produced.

'I'he above and other objects and advantages of the present invention 'will be apparent from a description of the process taken from the drawing,

which represents a flow diagram of the apparatus necessary for carrying out the present invention.

In the drawing, 10 represents a container for mixing the saponication charge consisting of fats, alkalies, water and oil. The mixer is provided with a mechanical agitator having paddles 11 xed on shaft 12 and rotated by gears 14 connected to a suitable source of power. The container is also provided with a perforated pipe 15 controlled by a valve 16 for introducing compressed air into the container, also for the purposek of agitating the ingredients forming the saponiflcation charge.

A line 20 provided with a pump 21 and a valve izo '1,971,760 22 connects with a closed steam jacketed pressure saponincation kettle 25. The closed kettle is provided with agltating paddles 26 mounted on shaft 27 and'connected by gears 28 to a suitable source of power. A scraper 29 is also fixed to one end of theshait 27 and is employed for preventing the ingredients from accumulating at the bottom of the kettle. Line 30 is for the purpose of introducing heating iiuid, such as steam, into the jacket 31, which is exited via line 32. A line 33 controlled by valve 34.is connected to the top of the kettle for the introduction of air or other gas into the kettle for increasing the pressure therein when desired. l

The bottom of the pressure kettle is provided with an outlet 35 which is controlled by a valve 36. Line 37 provided with a pressure reducing valve 38 connects the pressure kettle to a semijacketed and open compounding kettle 40. This kettle is also provided with agitating paddles41 fixed on shaft 42, which is connected by gears 43 to a. suitable sourceof power. Scrapers 44 are also fixed to one end of the shaft at the bottom of the kettle. Line 45 'permits the introduction of heating or cooling fluids, such as steam or water, into the jacket 46. They exit via line 47.

The bottom of the compounding kettle is provided with an outlet 48 controlled by valve 49 and connected to line 50.

In carrying out the process, the soap making ingredients are placed in the mixer 10 and are intimately mixed by the paddles 11 and/or by compressed air introduced through line 15. Various oils or fats of either animal or Vegetable origin may be employed, such as prime tallow, cottonseed oil, lard oil and olive oilor mixtures thereof. I prefer to employ a mixture of prime tallow and cottonseed oil. A suitable quantity of alkali, such as hydrated lime, caustic alkali or the like, or mixtures thereof is added, depending on whether a sodium soap grease or a calcium soap grease is to be formed. Water is then added in such quantity to effect complete saponication but not more than that required to finish the grease to the proper grade. I prefer to add only that required to completely sapomfy the fats and to bring the grease to the proper consistency so that `no water need be added during the subsequent compounding with the mineral oil. The amount of water which should be added may be predetermined either by experimentation or by calculation, as anyone skilled in the art will readily understand. A small amount of mineral oil should also be added in order to prevent the mass from bunching or lumping. During agitation and mixing, pump 21 and valve 22 are closed. After the ingredients have been thoroughly mixed, valve 22 is opened and pump 21 is started andthe mass is transferred via line 20 to the pressure kettle where the charge is heated for a period of about two hours under pressure. The heat is supplied by steam at -120 pounds per square inch introduced into the jacket 31. The temperature maintained in the kettle may vary from over 220 F. to 350 F. or higher, depending upon the pressure inside the kettle. This pressure may vary from 15-75 pounds per square inch and higher and may be aided by the introduction of gas, such as air, through line 33. During the heating the contents are continuously agitated by paddles 26. It should be understood that during the heating operation, no water should be permitted to escape. The reaction mixture has been calculated so that at the end of the saponication reaction the water content of the reacting mass will be avpredetermined amount. This can be determined by both stoichiometric calculation or by test if the compositions of the ingredients are known.

After saponiilcation has been completed, the charge is transferred via line 37 through the pressure reducing valve 38 into a body of a suitable quantity of mineral oil maintained in the compounding kettle 40. This' oil is employed for reducing the soap to the desired grade of grease, i. e., to distribute the soap throughout the oil and thus to form a homogeneous mass and to supply the lubricating constituents of the grease. An oil with a viscosity of from -200 seconds Saybolt at 100 F. and at a temperature of 14o-160 F. may be successfully used for this purpose. It is preferable to maintain a slightly smaller amount of oil in the compounding kettle 40. The discharge of the soap into the compounding kettle 40 should be carried out at a somewhat retarded rate in order to avoid blowing of the soap into the air above the oil in the open kettle. During this operation, the paddles in the open kettle should be kept in motion inorder to4 incorporate the soap into the oil as fast as it is discharged thereinto. This operation should require about 20-30 minutes. The temperature of the mass after complete discharge of the soap into the oil should be approximately 175 F., and preferably not over that at which evaporation and loss of water takes place. However, this temperature may be increased and yet evaporation avoided by providing a closed mixer and discharging and mixing the soap and oil under pressure. If the temperature is increased beyond that which is desirable, cooling water may be circulated through the jacket. After an additional twenty minute period of agitation, proper amounts of dye and oil of mirbane are added, after which the mass is brought to the proper consistency by the incorporation of the additional amount of mineral oil. The batch is then adjusted to the proper drawing temperature and is drawn.

As a speciiic example for carrying out this process, I have produced an excellent grade of grease by first saponifying a mixture of 220 pounds of prime tallow or 61.2% of the saponication charge, 25 pounds or 6.9% of cottonseed oil, 35 pounds or 9.7% of hydrated lime, 75 pounds or 20.8% of a mineral oil having a viscosity of 100 seconds Saybolt at 100 F. and 5 pounds or 1.4% of water. The above charge was rst thoroughly mixed and was then introduced into the pressure kettle where it was heated by superheated steam at a pressure. of 100 pounds per square inch circulated through the jacket for a period of two hours While continuously agitating the charge. During this time the pressure in the kettle rose to approximately 35 pounds per square inch and the temperature to 285 F. This chargeI formed about 360 pounds of soap having only a trace of free lime and no free fatty acids and a water content of 1.8%. The soap was gradually discharged into the compounding kettle, which was provided with 910 pounds of mineral oil at a temperature of 149 F. and having a viscosity of 100 seconds Saybolt at 100 F. During the gradual discharge of the soap into the oil, the paddles were kept in motion and the soap was thereby incorporated into the oil as fast as it was discharged. The discharging operation consumed about twenty to thirty minutes. The temperature of the mass rose to about 180 F. During anadditional period of twenty minutes of agitation, the temperature was increased to about 190- 200 F. An additional amount of water was added to give the grease a moisture content of 1.7%. 'I'he proper amounts of dye and oil of mirbane were then added, and the grease was then brought to the proper consistency by the additional incorporation of about 50 pounds of the above mineral oil. The batch was then adjusted to a drawing temperature of about 190 F. and drawn. The grease produced in this case had a smooth and glossy appearance of normal color and had a rm body.

While it is preferable to add 'substantially all of the water to the soap stock necessary for hydrolysis of the fats and for consistency grading, it is apparent that a smaller amount of water may be added to the saponiflcation charge, but of sufficient quantity to accomplish complete saponication. The saponication rate and its completion can be controlled by raising the temperature and by additionally increasing the pressure above the vapor pressure of the mixture by imposing additional air pressure. The remaining portion may then be added during compounding in the open kettle.

Thus, I have produced a good grade of grease by reducing the quantity of Water initially added to the saponiflcation charge in the above example from 5 pounds or 1.4% to about 0.9 pounds or 0.3% of the total saponication charge. In this case, the' soap which is produced had no free alkali present and only a trace of free fatty acids. The remaining water was then added in the compounding kettle to give the grease a moisture content of 1.7%. 'I'he grease produced was darker than that produced in theV preceding example, but otherwise was very good.

It is thus apparent that many modications may be made in controlling the amount of Water to be added during saponication and compounding with mineral oil. However, the amount of water preliminarily added to the saponication charge should never exceed that required in the finished grease so that it becomes necessary to evaporate or remove the excess before the compounding step. Nor should this amount be less than that necessary for complete saponication or hydrolysis.

Many modifications may be made for compounding the mineral oil with soap. Thus, instead of introducing the soap directly into a body of oil in the compounding kettle, the oil may be injected into the discharging line from the pressure kettle and the mixture then passed into the compounding kettle. If desired, a cyclic circulation of the mixture in the compounding kettle may be effected by pumping the mass from yassociated with the soap.

the bottom of the kettle to the top. Also, the soap may be cooled to a temperature below where water is evaporated before it is mixed in the open kettle. This also willprevent loss of Water. Many other methods for compounding the soap and oil will be apparent to those skilled in the art.

While an open compounding kettle has been disclosed and described for carrying out the compounding operation, it will be observed that the reduction of the soap in the oil may be carried out under pressure. Thus, the kettle 40 may constitute a closed vessel wherein the compounding may be carried out under pressure or by providing a saponification pressure kettle 25 of sufficiently large capacity, the mineral oil may be compounded therein without necessitating an additional compounding kettle. If desired, part of the oil for compounding may be introduced into the pressure kettle and the remaining portion in the open. or closed compounding kettle. Other variations 95 in this respect will be also apparent to those skilled in the art.

The above description is not to be taken as limiting my invention, but merely as illustrative of the invention and the best mode of carrying it out. Many changes can be made within the scope of the invention which I claim to be:

1. A process for the manufacture of a lubricating grease comprising preparing a soap by complete saponication in the presence of water at a temperature above the boiling point of water with avoidance of appreciable loss of said water, the amount of said Water being not in excess of that necessary in the nished grease, and directly injecting the hot soap and contained water into a body of oil below the surface thereof, the temperature of the oil being maintained below that at which appreciable loss of water would occur so as to condense and retainin the oil the water 2. The process for the manufacture of a lubricating grease comprising preparing a soap by complete saponiication in the presence of water at a temperature above the boiling point of water, and under preure, with avoidance of .appreciable loss of said water, the amount of said water being not in excess of that necessary in the nished grease, reducing the pressure, and directly injecting the hot soap and contained Water into a body of oil below the surface thereof, the temperature of the oil being maintained below that at which appreciable loss of Water would occur so as to condense and retain in the oil the water associated with the soap.

PHILIP SUBKOW. 

